TRUSS(1) BSD General Commands Manual TRUSS(1)NAME
truss -- trace system calls
SYNOPSIS
truss [-facedDS] [-o file] [-s strsize] -p pid
truss [-facedDS] [-o file] [-s strsize] command [args]
DESCRIPTION
The truss utility traces the system calls called by the specified process or program. Out-
put is to the specified output file, or standard error by default. It does this by stopping
and restarting the process being monitored via ptrace(2).
The options are as follows:
-f Trace descendants of the original traced process created by fork(2), vfork(2), etc.
-a Show the argument strings that are passed in each execve(2) system call.
-c Do not display individual system calls. Instead, before exiting, print a summary
containing for each system call: the total system time used, the number of times the
call was invoked, and the number of times the call returned with an error.
-e Show the environment strings that are passed in each execve(2) system call.
-d Include timestamps in the output showing the time elapsed since the trace was
started.
-D Include timestamps in the output showing the time elapsed since the last recorded
event.
-S Do not display information about signals received by the process. (Normally, truss
displays signal as well as system call events.)
-o file
Print the output to the specified file instead of standard error.
-s strsize
Display strings using at most strsize characters. If the buffer is larger, ``...''
will be displayed at the end of the string. The default strsize is 32.
-p pid Follow the process specified by pid instead of a new command.
command [args]
Execute command and trace the system calls of it. (The -p and command options are
mutually exclusive.)
EXAMPLES
# Follow the system calls used in echoing "hello"
$ truss /bin/echo hello
# Do the same, but put the output into a file
$ truss -o /tmp/truss.out /bin/echo hello
# Follow an already-running process
$ truss -p 34
SEE ALSOkdump(1), ktrace(1), ptrace(2)HISTORY
The truss command was written by Sean Eric Fagan for FreeBSD. It was modeled after similar
commands available for System V Release 4 and SunOS.
BSD May 12, 2009 BSD